/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package cn.cloud.all.security.core;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Annotation that is used to resolve {@link Authentication#getPrincipal()} to a method
 * argument.
 *
 * @author Rob Winch
 * @since 4.0
 * <p>
 * See: <a href=
 * "{@docRoot}/org/springframework/security/web/method/annotation/AuthenticationPrincipalArgumentResolver.html"
 * > AuthenticationPrincipalArgumentResolver </a>
 */
@Target({ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AuthenticationPrincipal {

    /**
     * True if a {@link ClassCastException} should be thrown when the current
     * {@link Authentication#getPrincipal()} is the incorrect type. Default is false.
     */
    boolean errorOnInvalidType() default false;

    /**
     * If specified will use the provided SpEL expression to resolve the principal. This
     * is convenient if users need to transform the result.
     *
     * <p>
     * For example, perhaps the user wants to resolve a CustomUser object that is final
     * and is leveraging a UserDetailsService. This can be handled by returning an object
     * that looks like:
     * </p>
     *
     * <pre>
     * public class CustomUserUserDetails extends User {
     *     // ...
     *     public CustomUser getCustomUser() {
     *         return customUser;
     *     }
     * }
     * </pre>
     * <p>
     * Then the user can specify an annotation that looks like:
     *
     * <pre>
     * &#64;AuthenticationPrincipal(expression = "customUser")
     * </pre>
     *
     * @return the expression to use.
     */
    String expression() default "";
}
